Thickened or gel laundry products are preferred by many consumers, over either powder or liquid detergents. Gels provide the advantages of liquid detergents, but also can be used for pretreatment of fabrics, obviating the necessity for purchase of a separate pre-treatment product.
Gel detergents have been described. See, for instance, WO 99/06519 and WO 99/27065, Klier et al. (U.S. Pat. No. 5,538,662), GB 2 355 015, Lance-Gomez et al. (U.S. Pat. No. 5,820,695), Hawkins (U.S. Pat. No. 5,952,285), Akred et al. (U.S. Pat. No. 4,515,704), Farr et al. (U.S. Pat. No. 4,900,469).
When a gel is made in a typical thin liquid mixer (i.e., a tank mixer) its shear-thinning characteristic does not allow for homogeneous mixing. The high shear portions of the mixer thin out the gel and are highly mixed areas. The low shear areas barely move—the gel thus creating a disproportionate mixture as ingredients are added. The mixture is made even more disproportionate by the typical method of ingredient addition, e.g. from dilute to rich. The disproportion causes areas of the gel mixture to rise high in viscosity (lumps), thus creating extended and unknown mix times. These typical liquid mixers, their methods of use and the additional mixing needed in them results in entraining air in the gel that cannot or easily be removed. Similar problems exist post mixing. Since the gel is high viscosity at low shear conditions, it is difficult to prime a pump—thus, typical liquid pumps cannot be used. There is also a greater chance of aeration when pumping and moving the gel because of its physical characteristics. Furthermore, if other minor ingredients are post dosed into the gel, extreme methods and/or large amounts of time are required to make a uniform product, due to the gel being shear-thinning. The gel is also harder to clean off the process equipment—thus, increased cleaning times and ingredients needed. Making the gel by using a tank mixer designed for use with liquids still involves a myriad of manufacturing issues dealing with post dosing, pumping, storing and aeration.